Method of making insulators



Aug. 14. 1928. I 1,680,705 E. THOMSON METHOD OF MAKING INSULATORS Filed Nov. 29. 1922 [/7 Veh 160/,- E///7. Thomson +775 fito'rna Patented Aug. 14, 1928.,

UNITED "STA E PATENT OFFICE.

, ELIHU THOMSON, OF SWAMPSGOTT, MASSACHUSETTS, ASSIGNOR 'IO GENERAL ELEO- TRIO COMPANY, A. CORPORATION OF NEW YORK.

'- METHOD OE MAKING INSUL A TORS.

Application filed November 29, 1922, serial mafeceon During recent years and, especlally since the introduction of the suspension system of supporting high potential electric lines, the ma ority of strain insulators used have been of the cemented cap and pin type, that is to say, the insulative member of orcelain has a cup-shaped part, to the outsi e ofwhicha' metal cap is cemented and to the inside of which a metal pin or bolt is cemented. After a cemented strain insulator has been in use two or three years, there develops a very pronounced tendency to fail b breakage ,of the 'orcelain and this fai ure has been general y attributed to the progressive hydration of the cement and the unequal coeflicients of expansion possessed by the close- -ly united metallic and non-metallic parts Many attemptshave been made to provide a satisfactory mechanical connection between the parts of strain insulators in an endeavor to avoid the practical defects of the cemented insulators, but 'none of them up to the present time have been elfective in displacin that type to a-material degree, for they eit er require the porcelain to be made in such complex shapes that a uniformly satisfactory product is rendered difficult of accomplishment or else the mechanical connection parts work loose or the porcelain part breaks by reason of the bearing of the metal parts thereon being localized instead of'distributed as in the case of the cemented type.

In carrying out my invention, I employ a vitreous insulative member of the cap and pin type having a bore or opening with an 1 enlargement to provide an internal shoulder insulators, it is impractical to pour molten metal onto or into them without-breakage. Moreover, by reason of the great stresses imposed upon strain insulators in use, it is highly desirable that the hardware'be of a strong hard metal, such as, iron or an alloy thereof, the melting point of which is higher than that of the usual insulatingtsubstances f I [have found that insulators of fused quartz have. such a; low coefiicient' of ex-' 1 pension and extremely. high melting point that molten iron or'iro'n alloy can be poured 7 into a ,cayity" therein wlthout injury to the insulatorandlthatiit is also practical to insert. a bar of iron orsteel-into the cavity'of 7 a quWt Zunsulator and bring it to a molten condition, therein by,v application, of heat.v to

'theexterior of the quartz insulator without injury"to the latter; a

. In the accompanying drawing,'I have in- 5 dicated the simplest embodiment of'my invention and certain steps'by which it is made, Fig. 1 is anaxial section of the strain insulator; Figs? and 3 are axial sectionsof'the fusedIqua-rtz insulator showing how a metalbolt or pin is cast therein; Figs. 1

4 and 5 are. similar views showing how an iron bar is'molded at its lower end'to fill the cavityfof the insulator; and Figs. 6 and 7 indicate separate steps inthe formation of a quartz insulator member.

As indicated in Fig. 1, the insulating member 1 of fused quartz has a hollow globular head2 having an internal shoulder anda tubular stem 3 within which a rear with 40 an expanded head 5 is located, whilethe outside of the globular head 2 is received between an annular seat plate 6 and a supporting yoke 7 held together by rivets or i 4 The free ends of the yoke 7 and the bolt-4 5e are provided with suitable means'fsucn as eyesor-threads for attachment of the insulator to the stress applying device,

To cast a bolt 4 in a quartz insulating member 1, the latter is positioned with head down 10-0 and the stem lengthened in efiect by a detachable extension cylinder '9 and the entire cavity filled with molten metal. The exten sion cylinder 9 is removed after the metal is cooled so as to expose a corresponding length of the bolt beyond the end'of the insulating member 1, in which a thread 10 ma be out.

To u set or mold the end of a p ain iron, bar' wit in the quartz insulatin' member, a bar with excess length is intro need within the hollow of the insulating member, as indicated in Fig. 4, and heat applied to the outside of the head 2 of the latter until it is raised to a' sufficiently high temperature to soften or melt the end of the contained bar which then settles until the hollow of the lrl ead 2 is filled with metal, as indicated in i 5. a

pon allowing to cool, the cast or molded metal shrinks away from the wall of the insulator sufiiciently to upset any tendency to adhere thereto. I

While the insulating member 1 may be a made in various shapes, theplain one shown is very satisfactory in service and can be manufact-uredof fused quartz very economi-' cally. I make a carbon core 11 approximately the same size as the pin or'bolt 4, connect its ends to metallic electric conductors, embed it in quartz grains, and raise the temperature thereof. tothe fusion point of quartz by passing a strong electric current through it for a suflicient. period of time to produce an encrustation of quartz thereabout of the desired th'ckness. When the fused quartzencrustatio or shell is cooled; or practically cooledyitis removed from the bed of quartz grains and has the'appearance indicated in Fig; '6 The carbon core 11 is reinsulators comprising .tension membe homogeneously united at any desired point thereon by fusion.

Although I have shown and described only oneembodiment of the invention, I do not desire to be restricted thereto.

,What I claim as new and desire to secure by Letters Patent of the United States, is,

1. The. method of making electric insulators comprising the forming of an insulatin member of fused quartz with a. bore an forming therein by fusion a metallic pin.

2. The method of making electric strain the forming of an insulating member 0 fused quarts with a bore therein enlarged to provide an internal shoulder, and forming in said bore a metallic I In witness whereof, I have hereunto set my hand this 24th 'day of November, 1922.

' ELIHU THOMSON. 

